1. Field of the Invention
The present invention concerns a device to recover the paint from belt conveyors supporting and moving the objects to the painted in automatic spray painting plants.
The problem to be faced in the aforespecified conveyors mainly involves the smearing of the conveying means, determined by the paint being sprayed which misses the object to be painted--thereby adhering to said means--and cannot be recovered. The smearing of the conveyor and the failure to recover the paint missing the objects to be painted give rise to various negative consequences and should hence be eliminated as far as possible.
Among the most important of these consequences, the following should be particularly remembered:
the drying up of the paint creates obstacles and hinders the regular working of the movable elements of the conveyor; PA1 the waste of a considerable amount of paint, which may reach even 40-50% of the total amount of paint used; PA1 the smearing of the objects to be painted, subsequently positioned on the conveyor, by the paint deposited thereon and not yet fully dried, when the conveyor is not constantly and perfectly cleaned therefrom; and finally, PA1 the ecological consequences deriving from the elimination of the paint scattered on the conveyor and not recovered.
The device according to the present invention allows to efficiently and automatically recovering the excess paint sprayed onto the conveyor belt around the object being painted, while considerably reducing the stresses imparted to said belt as compared to the known type paint recovery devices.
2. Description of the Prior Art
The systems currently adopted for cleaning belt conveyors consist of fixed or oscillating scraping elements, which act on the surface of the belt conveyor, both in the event of this latter being a single steel or synthetic material belt, and in the event that it should instead be formed of a plurality of steel strips. These scraping elements usually consist of a flexible blade of steel, when the belt is formed of steel, or of a plastic beak-shaped section, when the belt is of plastic material. In both cases, in order to obtain a proper cleaning of the belt, the scraping means are pressed into contact with the belt surface with a high pressure, so that the scraping action determined by the contact may totally remove the excess paint applied when spraying.
Nevertheless, the aforedescribed paint recovery devices suffer from a great number of drawbacks, which have limited their application and have led users to adopt protection systems for the conveyor belt, which make use of expendable materials protecting the belt from paint deposits and being renewed at each painting cycle.
A first drawback of the known paint recovery systems is the incomplete and irregular removal of the drying paints due to their high viscosity. The paint recovery device is in practice positioned at a certain distance from the painting area (normally in correspondence of the return part of the belt), and during the time taken for the belt to cover this distance the sprayed paint has already lost a considerable amount of solvents, consequently increasing its viscosity and making it difficult to entirely remove it from the belt. For the same reason, the removed paint does not easily drop from the scraping means which become, more or less rapidly, covered with paint, making it even more difficult to remove the paint from the belt. Furthermore, in case of stopping of the plant, the paint accumulated on the scraping means quickly becomes solid, causing said means to stick to the belt and making it hence indispensable to stop the plant even longer for cleaning.
To try to overcome the above problem--making it thus possible to remove the already partially dried and thus particularly viscous paints--it is known to increase the pressure of the scraping means on the belt to rather high values. This however creates other inconveniences. On the one hand, the wear by friction of the belt and of the actual scraping means is in fact strongly accelerated, to the extent that, in order to prevent irregular wear--and thus an irregular cleaning of the belt--an oscillating movement in a direction transverse to the movement of the belt is often imparted to the scraping means. On the other hand, the friction between the scraping means and the belt results in; a considerable waste of energy, with a consequent requirement to oversize the power of the motor driving the belt.